Field of the Invention
Aspects of the present invention relate generally to a wireless communications system, and more particularly, to a method and a communications device for improving frequency band support.
Description of the Related Art
The term “wireless”, normally refers to an electrical or electronic operation, which is accomplished without the use of a “hard wired” connection. “Wireless communications” is the transfer of information over a distance without the use of electrical conductors or wires. The distances involved may be short (a few meters for television remote controls) or very long (thousands or even millions of kilometers for radio communications). The best known example of wireless communications is the cellular telephone. Cellular telephones use radio waves to enable an operator to make phone calls to another party, from many locations world-wide. They can be used anywhere, as long as there is a cellular telephone site to house equipment that can transmit and receive signals, which are processed to transfer both voice and data to and from the cellular telephones.
There are various well-developed and well-defined cellular communications technologies. For example, the Global System for Mobile communications (GSM) is a well-defined and commonly adopted communications system, which uses time division multiple access (TDMA) technology, which is a multiplex access scheme for digital radio, to send voice, data, and signaling data (such as a dialed telephone number) between mobile phones and cell sites. The CDMA2000 is a hybrid mobile communications 2.5 G/3G (generation) technology standard that uses code division multiple access (CDMA) technology. The UMTS (Universal Mobile Telecommunications System) is a 3G mobile communications system, which provides an enhanced range of multimedia services over the GSM system. The Wireless Fidelity (Wi-Fi) is a technology defined by the 802.11 engineering standard and can be used for home networks, mobile phones, video games, to provide a high-frequency wireless local area network. The LTE (Long Term Evolution) and the LTE-Advanced evolved from the LTE is a 4G mobile communications system, which provides a high-speed data transmission over the 2G and 3G system.
Generally, a registered public land mobile network (RPLMN) can support multiple frequencies. When a user equipment (UE) camps on the UMTS network which provides for wrong system information block (SIB) 19 for reselecting to the LTE network, the UE cannot reselect back to the LTE network even though the UE tries to turn on/off the airplane mode. More specifically, the current communications specification defines that the system information of the UMTS which the UE camps on will be saved in the RPLMN when the UE is turned off. However, the UE still camps back on the same cell which provides the wrong system information when the UE is rebooted. The case described above may result in the UE using the wrong system information, and cannot re-select back to the LTE network.
Thus, there is a need for a method and a device for improving frequency band support to solve the above problems.